How to troubleshoot forwarder management not showing any clients?

[NeedNotToKnow]

How can I troubleshoot the deployment server or universal or heavy forwarder?

I set up deployment server then in forwarders I run ./splunk set deploy-poll ip:port 

But Forwarder Management clients = 0!

Why? How can I troubleshoot it and solve it?

in forwarder:

cat /opt/splunkforwarder/etc/system/local/deploymentclient.conf

[target-broker:deploymentServer]
targetUri = X.X.X.58:8089

in deployment-server:

/opt/splunk/bin/splunk list deploy-clients

WARNING: Server Certificate Hostname Validation is disabled. Please see server.conf/[sslConfig]/cliVerifyServerName for details.
No deployment clients have contacted this server.

Note: the forwarder and deployment server in Google Cloud VMs

Note: I tried it on a local server, and it's running right

can anyone help me? 

[richgalloway · Accepted solution]

Verify the forwarders are allowed to connect to port 8089 on the DS.

Look in splunkd.log on the forwarders for connection/protocol errors.  They'll probably come from the "DC" component.

[NeedNotToKnow]

Thank you, the problem is solved

sorry for that, but the firewall was denying 8089.